1. Field of the Invention
The present invention generally relates to grinding tools, and more particularly to grinding tools used in wafer polishing techniques.
2. Description of the Related Art
Grinding and/or polishing techniques are generally applied to create a desirable surface roughness or planarity of a rigid part, such as metal, ceramic or glass parts, or semiconductor wafers. To this purpose, the grinding and/or polishing techniques use tools having abrasive elements that can wear the rigid surface.
During the fabrication of a grinding tool, the abrasive elements are conventionally affixed to a substrate of the grinding tool by sintering or brazing. This high-temperature process may cause thermal deformation of the substrate, which may result in a non-uniform height of the abrasive elements attached thereon. In order to reduce thermal deformation, the material of the substrate needs to be properly selected, which may add constraints to the fabrication process.
According to another approach, an adhering agent may be used to bind the abrasive elements to the working surface of the substrate. However, owing to the melt flow of the adhering agent and the contraction mismatch between the adhering agent and the substrate, it may be difficult to control the height of the abrasive elements adhered to the substrate.
In a conventional grinding tool, the substrate with the abrasive elements affixed thereon is further attached to a support member by heat press. As the substrate may be subject to warping during thermal stress, some approach also proposes to provide an additional layer of abrasive elements affixed on the other side of the substrate opposite to the working surface. The distribution of two layers of abrasive elements on two opposite sides of the substrate can help to keep the substrate planar during thermal stress. However, it has been observed that in practice a totally flat substrate may not be able to tightly adhere to the support member, which may eventually result in a grinding tool that has a non-uniform height of the abrasive elements on the working surface.
Therefore, there is a need for an improved design that can fabricate a grinding tool having abrasive elements of a uniform height on the working surface, and can address at least the foregoing issues.